Pigments and polymer composites formed thereof

ABSTRACT

A composite material includes a polymer matrix and a pigment dispersed in the polymer matrix. The pigment includes an alumina hydrate particulate material and a dye. The dye is covalently bonded to a surface of the alumina hydrate particulate material.

FIELD OF THE DISCLOSURE

The present application is related generally to polymer composites andpigments.

BACKGROUND

In general, colored plastics or polymer materials are desirable for usein a variety of applications, such as plastic consumer products andpolymer composite building materials. Such colored plastics and polymermaterials provide improved appearance and aesthetic character to theobjects into which they are formed. Typically, pigments or dyes areadded to polymer materials to produce the colored polymer materials.

However, traditional colored polymer materials can fade, lose color, orundergo aesthetically displeasing color changes. Traditional dyes mayleach from the polymer material or may lose color or bleach throughthermal degradation or degradation caused by exposure to radiation, suchas ultraviolet electromagnetic radiation. Leaching is a particularproblem for dyes blended in halogenated polyolefins. As such, polymermaterials including such dyes may have poor color fastness.

In addition, dispersion of traditional pigments with polymer materialsis difficult. Poor dispersion leads to swirling and color variabilitywith the colored polymer material. Further, poor dispersion of thepigment within the plastic article may lead to undesirable mechanicalproperties. As such, compatibilizers are typically used to dispersepigment within a polymer material. Such compatibilizers include avariety of organic compounds that aid in dispersing the pigment. Inaddition, pigments are dispersed using high shear mechanical processes.However, compatibilizers typically are expensive and may also influencemechanical properties of the colored polymer material.

Accordingly, there is a continued need within the industry to providepigments and plastics having improved fastness, stability and resistanceto bleaching and color leaching.

SUMMARY

In a particular embodiment, a pigment includes an alumina hydrateparticulate material and a dye. The dye is covalently bonded to asurface of the alumina hydrate particulate material.

In another exemplary embodiment, a composite material includes a polymermatrix and a pigment dispersed in the polymer matrix. The pigmentincludes an alumina hydrate particulate material and a dye. The dye iscovalently bonded to a surface of the alumina hydrate particulatematerial.

In a further exemplary embodiment, a composite material includes apolymer matrix incorporating a pigment. The pigment includes a triazinedye covalently bonded to a surface of a boehmite particulate material.The boehmite particulate material has a specific surface area notgreater than about 250 m²/g and has an average particle size not greaterthan about 1000 nm.

In an additional embodiment, a method for forming a pigment includesproviding a slurry comprising an alumina hydrate particulate materialand adding a dye and the slurry to form a pigment slurry. The dyeincludes a functional group configured to facilitate covalent bondingwith a surface group of the alumina hydrate particulate material.

In a further embodiment, a method of forming a composite materialincludes mixing a pigment and a polymer to form a polymer mixture. Thepigment includes an alumina hydrate particulate material and a dyecovalently bonded to a surface group of the alumina hydrate particulatematerial. The method also includes melting the polymer mixture to formthe composite material.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIGS. 1, 2, 3, and 4 include illustrations of material properties, suchas relative flex modulus, impact strength, relative percentcrystallinity, and T50, of an exemplary polymer composite.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DESCRIPTION OF THE DRAWINGS

In a particular embodiment, a composite material is formed of a polymermatrix and a pigment. The pigment includes alumina hydrate particulatehaving a dye covalently bonded to the surface of the alumina hydrateparticulate. For example, the dye may be covalently bonded in place of ahydrogen and to an oxygen of a hydroxyl surface group of the aluminahydrate particulate. In an exemplary embodiment, the polymer matrix isformed of a polyolefin or a halogenated polyolefin.

In another exemplary embodiment, a method of forming a pigment includespreparing a slurry including alumina hydrate particulate material. Themethod further includes adding dye to the slurry to form a pigmentslurry. The dye has a functional group configured to facilitate covalentbonding with the alumina hydrate particulate material, such as with ahydroxyl group on the surface of the alumina hydrate particulatematerial. Once formed, the pigment slurry may be dried and milled toproduce the pigment. In a particular embodiment, the pigment may beblended with a polymer material, such as a thermoplastic polymer, andextruded or melt blended to form a composite material.

In an exemplary embodiment, the composite material includes a polymermatrix and a pigment dispersed in the polymer matrix. The polymer matrixmay be formed of a thermoplastic polymeric material or of a thermosetpolymeric material. In an example, the polymer matrix is formed of athermoplastic polymer, such as a polyolefin or a halogenated polyolefin.For example, the thermoplastic polymer may include a polymer, a polymerblend, or a copolymer formed from a monomer, such as ethylene,propylene, vinyl chloride, vinylidene chloride, vinyl fluoride,vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene orcombinations thereof. As such, a thermoplastic polymer may includepolyethylene, polypropylene, polyvinylchloride (PVC),polyvinylidenechloride (PVDC), polyvinylflouride (PVF),polyvinylidenefluoride (PVDF), polytetrafluoroethylene (PTFE),polychlorotrifluoroethylene (PCTFE), or combinations thereof. In afurther exemplary embodiment, the thermoplastic polymer may include apolymer, a polymer blend, or a copolymer including a polyacrylate, suchas polymethylmethacrylate (PMMA), polymethyl acrylate (PMA), polyacrylicacid (PAA), polybutyl acrylate (PBA); a polyamide, such as nylon 6,nylon 11, nylon 12; a polyester, such as polyethylene terephthalate(PET), or polybutylene terephthalate (PBT); a polyurethane; apolycarbonate; or cellulose, including esters or nitrates thereof. In anadditional example, the thermoplastic polymer may be a polymer, apolymer blend, or a copolymer including ethyl vinyl acetate (EVA), ethylvinyl alcohol (EVOH), ethylene propylene diene monomer (EPDM),polymethylpentene (PMP), polyethylene oxide (PEO), orpolyetheretherketone (PEEK).

Alternatively, the polymer matrix may be formed of a thermoset polymer.For example, the polymer matrix may be formed of a polymer, such asepoxy, phenolic resin, melamine, furan, urea-formaldehyde, polyurethane,silicone, vinyl ester, or unsaturated polyester resin.

In an exemplary embodiment, the composite material includes a pigmentdispersed in the polymer matrix. The pigment includes alumina hydrateparticulate material having a dye covalently bonded to the surface ofthe alumina hydrate particulate.

In general, the alumina hydrate particulate material includes hydratedalumina conforming to the formula: Al(OH)_(a)O_(b), where 0<a≦3 and b=(3−a)/2. In general, the alumina hydrate particulate material has awater content of about 1% to about 38% by weight, such as about 15% toabout 38% water content by weight. In a particular embodiment, thealumina hydrate particulate material is free of non-alumina ceramicmaterials, and, in particular, is free of silica and aluminosilicatematerials. By way of example, when a =0 the formula corresponds toalumina (Al₂O₃).

Alumina hydrate particulate materials can include aluminum hydroxides,such as ATH (aluminum tri-hydroxide), in mineral forms known commonly asgibbsite, bayerite, or bauxite, or can include alumina monohydrate, alsoreferred to as boehmite. Such mineral form aluminum hydroxides can formalumina hydrate particulate material useful in forming the pigment orcan be used as an aluminous precursor, for further processing, such asin a seeded hydrothermal treatment, described in more detail below.

According to an embodiment, the alumina hydrate particles have an aspectratio, defined as the ratio of the longest dimension to the next longestdimension perpendicular to the longest dimension, generally at leastabout 2:1, and, in particular, at least about 3:1, such as at leastabout 4:1, or at least about 6:1. Particular embodiments have relativelyelongated particles, such as at least about 8:1, at least about 10:1,and, in particular examples, at least about 14:1.

With particular reference to the morphologies of the alumina hydrateparticles, different morphologies are available, such as needle-shaped,ellipsoidal-shaped, and platelet-shaped particles. For example,particles having a needle-shaped morphology may be further characterizedwith reference to a secondary aspect ratio defined as the ratio of thesecond longest dimension to the third longest dimension perpendicular tothe first and second longest dimensions. The secondary aspect ratio ofneedle-shaped particles is generally not greater than about 3:1,typically not greater than about 2:1, or not greater than about 1.5:1,and oftentimes about 1:1. The secondary aspect ratio generally describesthe cross-sectional geometry of the particles in a plane perpendicularto the longest dimension. It is noted that since the term aspect ratiois used herein to denote the ratio of the longest dimension to the nextlongest dimension, it may be referred as the primary aspect ratio.

According to another embodiment, the alumina hydrate particles can beplatey or platelet-shaped particles generally of an elongated structurehaving a primary aspect ratios described above in connection with theneedle-shaped particles. However, platelet-shaped particles generallyhave opposite major surfaces, the opposite major surfaces beinggenerally planar and generally parallel to each other. In addition, theplatelet-shaped particles may be characterized as having a secondaryaspect ratio greater than that of needle-shaped particles, generally atleast about 3:1, such as at least about 6:1, or at least about 10:1.Typically, the shortest dimension or edge dimension, perpendicular tothe opposite major surfaces or faces, is generally less than 50nanometers, such as less than about 40 nanometers, or less than about 30nanometers.

According to another embodiment, the alumina hydrate particles can beellipsoidal-shaped particles generally of an elongated structure havinga primary aspect ratio described above in connection with theneedle-shaped particles. In addition, the ellipsoidal-shaped particlesmay be characterized as having a secondary aspect ratio not greater thanabout 2:1, not greater than about 1.5:1, or about 1:1.

Morphology of the alumina hydrate particulate material may be furtherdefined in terms of particle size and, more particularly, averageparticle size. As used herein, the “average particle size” is used todenote the average longest or length dimension of the particles.Generally, the average particle size is not greater than about 1000nanometers, such as about 75 nanometers to about 1000 nanometers. Forexample, the average particle sizes may be not greater than about 800nanometers, not greater than about 500 nanometers, or not greater thanabout 300 nanometers. In the context of fine particulate material,embodiments have a particle size not greater than 250 nanometers, suchas not greater than 225 nanometers. Due to process constraints ofcertain embodiments, the smallest average particle size is generally atleast about 75 nanometers, such as at least about 100 nanometers, or atleast about 135 nanometers.

Due to the elongated morphology of the particles, conventionalcharacterization technology is generally inadequate to measure averageparticle size, since characterization technology is generally based uponan assumption that the particles are spherical or near-spherical.Accordingly, average particle size was determined by taking multiplerepresentative samples and physically measuring the particle sizes foundin representative samples. Such samples may be taken by variouscharacterization techniques, such as by scanning electron microscopy(SEM). The term average particle size also denotes primary particlesize, related to the individually identifiable particles, whetherdispersed or agglomerated forms. Of course, agglomerates have acomparatively larger average particle size, and the present disclosuredoes not focus on agglomerate sizing.

In addition to aspect ratio and average particle size of the aluminahydrate particulate material, morphology of the particulate material maybe further characterized in terms of specific surface area. Herein,specific surface area of the particulate material relates to specificsurface area as measurable by the commonly available BET technique.According to embodiments herein, the alumina hydrate particulatematerial has a specific surface area, generally not less than about 10m²g, such as not less than about 20 m²/g, 30 m²/g, or not less thanabout 40 m²/g. Since specific surface area is a function of particlemorphology as well as particle size, generally the specific surface areaof embodiments is not greater than about 250 m²/g, such as not greaterthan about 200 m²/g or not greater than about 100 m²/g. In particular,the surface area may be about 50 m²/g to 250 m²/g. In an exemplaryembodiment, needle shaped alumina hydrate particulate has a specificsurface area of about 100 m²/g to about 250 m²/g. In another exemplaryembodiment, platelet shaped alumina hydrate particulate has a specificsurface area about 50 m²/g to about 98 m²/g.

In a particular embodiment, when a is approximately one (1) within thegeneral formula: Al(OH)_(a)O_(b), where 0<a≦3 and b =(3−a)/2, thealumina hydrate material corresponds to boehmite. More generally, theterm “boehmite” is used herein to denote alumina hydrates includingmineral boehmite, typically being Al₂O₃.H₂O and having a water contenton the order of 15%, as well as psuedoboehmite, having a water contentgreater than 15%, such as 20-38% by weight. As such, the term “boehmite”will be used to denote alumina hydrates having 15% to 38% water content,such as 15% to 30% water content by weight. It is noted that boehmite(including psuedoboehmite) has a particular and identifiable crystalstructure, and accordingly unique X-ray diffraction pattern, and assuch, is distinguished from other aluminous materials including otherhydrated aluminas. Boehmite can be obtained by processing aluminousminerals, such as an aluminous precursor through a seeded processingpathway, to provide desirable morphology and particle characteristics.

According to one embodiment, the boehmite particles have an aspect ratioof at least about 2:1, and particularly at least 3:1, at least 4:1, orat least 6:1. Indeed, certain embodiments have relatively elongatedparticles, such as not less than 8:1, not less than 10:1, and in somecases, not less than 14:1. Like the aluminous materials previouslydiscussed, the boehmite has various morphologies, such as needle-shaped,ellipsoidal-shaped, and platelet-shaped particles.

Turning to the details of the processes by which the boehmiteparticulate material may be manufactured, generally ellipsoid, needle,or platelet-shaped boehmite particles are formed from a boehmiteprecursor, typically an aluminous material including bauxitic minerals,by hydrothermal treatment as generally described in the commonly ownedpatent described above, U.S. Pat. No. 4,797,139. More specifically, theboehmite particulate material may be formed by combining the boehmiteprecursor and boehmite seeds in suspension, exposing the suspension(alternatively sol or slurry) to heat treatment to cause conversion ofthe raw material into boehmite particulate material, further influencedby the boehmite seeds provided in suspension. Heating is generallycarried out in an autogenous environment, that is, in an autoclave, suchthat an elevated pressure is generated during processing. The pH of thesuspension is generally selected from a value of less than 7 or greaterthan 8, and the boehmite seed material has a particle size finer thanabout 0.5 microns. Generally, the seed particles are present in anamount greater than about 1% by weight of the boehmite precursor(calculated as Al₂O₃), and heating is carried out at a temperaturegreater than about 120° C., such as greater than about 125° C., or evengreater than about 130° C., and at a pressure that is autogenouslygenerated, typically around 30 psi.

The particulate material may be fabricated with extended hydrothermalconditions combined with relatively low seeding levels and acidic pH,resulting in preferential growth of boehmite along one axis or two axes.Longer hydrothermal treatment may be used to produce even longer andhigher aspect ratio of the boehmite particles and/or larger particles ingeneral.

Following heat treatment, such as by hydrothermal treatment, andboehmite conversion, the liquid content is generally removed, such asthrough an ultrafiltration process or by heat treatment to evaporate theremaining liquid. Thereafter, the resulting mass is generally crushed,such to 100 mesh. It is noted that the particulate size described hereingenerally describes the single crystallites formed through processing,rather than the aggregates, which may remain in certain embodiments(e.g., for those products that call for an aggregated material).

Several variables may be modified during the processing of the boehmiteraw material to effect the desired morphology. These variables notablyinclude the weight ratio, that is, the ratio of boehmite precursor toboehmite seed, the particular type or species of acid or base usedduring processing (as well as the relative pH level), and thetemperature (which is directly proportional to pressure in an autogenoushydrothermal environment) of the system.

In particular, when the weight ratio is modified while holding the othervariables constant, the shape and size of the particles forming theboehmite particulate material are modified. For example, when processingis performed at 180° C. for two hours in a 2 weight % nitric acidsolution, a 90:10 ATH:boehmite seed ratio forms needle-shaped particles(ATH being a species of boehmite precursor). In contrast, when theATH:boehmite seed ratio is reduced to a value of 80:20, the particlesbecome more elliptically shaped. Still further, when the ratio isfurther reduced to 60:40, the particles become near-spherical.Accordingly, most typically the ratio of boehmite precursor to boehmiteseeds is not less than about 60:40, such as not less than about 70:30 ornot less than about 80:20. However, to ensure adequate seeding levels topromote the fine particulate morphology that is desired, the weightratio of boehmite precursor to boehmite seeds is generally not greaterthan about 98:2. Based on the foregoing, an increase in weight ratiogenerally increases aspect ratio, while a decrease in weight ratiogenerally decreases aspect ratio.

Further, when the type of acid or base is modified, holding the othervariables constant, the shape (e.g., aspect ratio) and size of theparticles are affected. For example, when processing is performed at180° C. for two hours with an ATH:boehmite seed ratio of 90:10 in a 2weight % nitric acid solution, the synthesized particles are generallyneedle-shaped. In contrast, when the acid is substituted with HCI at acontent of 1 weight % or less, the synthesized particles are generallynear spherical. When 2 weight % or higher of HCl is utilized, thesynthesized particles become generally needle-shaped. At 1 weight %formic acid, the synthesized particles are platelet-shaped. Further,with use of a basic solution, such as 1 weight % KOH, the synthesizedparticles are platelet-shaped. If a mixture of acids and bases isutilized, such as 1 weight % KOH and 0.7 weight % nitric acid, themorphology of the synthesized particles is platelet-shaped. Noteworthy,the above weight % values of the acids and bases are based on the solidscontent only of the respective solid suspensions or slurries, and arenot based on the total weight % of the total weight of the slurries.

Suitable acids and bases include mineral acids such as nitric acid,organic acids such as formic acid, halogen acids such as hydrochloricacid, and acidic salts such as aluminum nitrate and magnesium sulfate.Effective bases include, for example, amines including ammonia, alkalihydroxides such as potassium hydroxide, alkaline hydroxides such ascalcium hydroxide, and basic salts.

Still further, when temperature is modified while holding othervariables constant, typically changes are manifested in particle size.For example, when processing is carried out at an ATH:boehmite seedratio of 90:10 in a 2 weight % nitric acid solution at 150° C. for twohours, the crystalline size from XRD (x-ray diffractioncharacterization) was found to be 115 Angstroms. However, at 160° C. theaverage particle size was found to be 143 Angstroms. Accordingly, astemperature is increased, particle size is also increased, representinga directly proportional relationship between particle size andtemperature.

According to embodiments described herein, a relatively powerful andflexible process methodology may be employed to engineer desiredmorphologies into the precursor boehmite product. Of particularsignificance, embodiments utilize seeded processing resulting in acost-effective processing route with a high degree of process controlwhich may result in desired fine average particle sizes as well ascontrolled particle size distributions. The combination of (i)identifying and controlling key variables in the process methodology,such as weight ratio, acid and base species and temperature, and (ii)seeding-based technology is of particular significance, providingrepeatable and controllable processing of desired boehmite particulatematerial morphologies.

The pigment is formed of an alumina hydrate, such as an alumina hydrateas described above, covalently bonded to a dye. In an exemplaryembodiment, the dye is an organic dye. For example, the dye may be anorganic dye, such as an anthracene dye, an azo dye, an acridine dye, anazine dye, an oxazine dye, a thiazine dye, a quinoline dye, apolymethine dye, a hydrazone dye, a triazine dye, a porphyrin dye, aporphyrazine dye, a sulfur dye, a quinacridone dye, a formazane dye, anitro dye, a nitroso dye, an azomethine dye or a polyol dye. In aparticular embodiment, the dye includes a triazine dye, such as CibacronHD200% (red), PBN-GR (red), C-2BL (red), FN-2BL (red), PB6R-GRl50%(brown), CB (navy), or FN-B (navy), each available from Ciba SpecialtyChemicals. In another embodiment, the dye includes a polyol dye.

In a particular embodiment, the dye includes a functional groupconfigured to facilitate covalent bonding with the alumina hydrate. Forexample, the functional group may undergo a reaction to form a covalentbond with oxygen of a hydroxyl group on the surface of the aluminahydrate particulate. In particular, the function group may facilitatenucleophilic substitution or nucleophilic addition with a hydroxyl groupon the surface of the alumina hydrate particulate, such as forming acovalent bond with oxygen of the hydroxyl group in place of thehydrogen. An exemplary functional group includes a halogen atom, such asfluorine, chlorine, or bromine. Another example of a functional groupincludes sulfatoethylsolfone. A further exemplary functional group mayinclude silanol, zirconate, titanate, carboxylic acid and esters,aldehyde, sulphonic acid, or phosphonic acid. Typically, the functionalgroup is attached to a carbon atom of the organic dye, such as a carbonatom of a functional ring of the organic dye. In a particularembodiment, the functional group is bonded to a carbon atom of thetriazine ring of the dye.

Evidence of the covalent bonding of the dye to the surface of thealumina hydrate particulate material, as opposed to a weak secondarybonding mechanism on the surface of the particle or an intercalationmechanism between the layers of a material, is illustrated in Table 1,provided below. Table 1 illustrates the average binding energy ofsurface aluminum atoms and oxygen atoms of an alumina hydrateparticulate material (in this case, boehmite) and compares these resultsto a sample containing boehmite and a dye. The average binding energiesof the surface aluminum and oxygen atoms are measured using Augerspectroscopy. Table 1 demonstrates an attenuation of the average bindingenergy of aluminum atoms and an increase in the average binding energyof oxygen atoms on the surface of the alumina hydrate particulatematerial after the addition of the dye, indicating covalent bondingbetween the dye and oxygen atoms on the surface of the boehmiteparticles. TABLE 1 Auger Spectroscopy of two samples demonstrating thechange in binding energies of Al and O atoms on the surface of theboehmite with the addition of a dye. Sample ID Al O Boehmite: BE (eV)1389.15 509.9 Atomic % 47.84 52.16 Boehmite + Dye BE (eV) 1388.94 510.34Atomic % 44.02 54.52

To form the pigment, the dye may be reacted with particulate aluminahydrate. For example, a slurry may be formed of the particulate aluminahydrate. The slurry may include an aqueous liquid or an organic liquid.In an exemplary embodiment, the slurry is an aqueous slurry thatincludes not greater than about 30 wt % alumina hydrate particulate,such as not greater than about 20 wt % or not greater than about 15 wt %alumina hydrate particulate. In a further exemplary embodiment, theslurry has a pH not greater than about 7.0, such as not greater thanabout 5.0.

In an exemplary method, the slurry is heated to within a range of about25° C. to about 100° C., such as about 40° C. to about 80° C. A dyehaving a functional group configured to facilitate covalent bonding tothe alumina hydrate is added to the slurry. In an exemplary embodiment,the dye may be included in a dye solution that is added to the slurry.In a particular example, the dye solution is an aqueous solutionincluding not greater than about 10 wt % dye. In another example, thedye may be a powder added to the slurry. The slurry may be mechanicallymixed or agitated.

Once the pigment has formed, the pigment may be dried. For example, thepigment may be spray dried. The dried pigments may be milled, such asthrough ball milling, to form a pigment powder.

When a thermoplastic polymer forms the polymer matrix, the method offorming the composite material includes dry mixing the polymer with thepigment to form a polymer mixture. The polymer mixture may be melt toform the composite. For example, the polymer mixture may be extruded.Alternatively, the polymer mixture may be melt blended.

When a thermoset polymer forms the polymer matrix, the method of formingthe composite material includes blending a pigment with a solution ofpolymer precursor. For example, a dry pigment may be mixed with thesolution under high shear conditions. In another example, a pigmentsolution may be mixed with the polymer precursor solution.

In an exemplary embodiment, the composite material includes about 2 wt %to about 25 wt % pigment. For example, the composite material includesabout 5 wt % to about 10 wt % pigment. In addition, the compositematerial may include about 60 wt % to about 98 wt % polymer material,such as about 70 wt % to about 95 wt % polymer material. While thecompositions are expressed in percentages, such as weight percentages,it is understood that specification of a percentage of a particularcomponent affects the percentage of other components within acomposition and in no way can the cumulative percentage of allcomponents be greater than one hundred percent.

In addition to the pigment, the composite may also includecompatiblizers, fillers, antioxidants, ultraviolet radiation absorbers,plasticizer or a combination thereof. For example, the composite mayinclude a plasticizer to improve processability. In another example, thecomposite may include an antioxidant or an ultraviolet radiationabsorber to improve weatherability. In a further embodiment, thecomposite may include a compatibilizer to improve compatibility betweenpolymers of a polymer blend or to improve dispersion of the pigment.Alternatively, the dye covalently bonded to the alumina hydrateparticulate may provide compatibilizing properties. In a particularembodiment, the composite is free of compatibilizer, while exhibitingequivalent or enhanced dispersion of the alumina hydrate particulate.

According to an exemplary embodiment,. a composite material including apolymer matrix and an alumina hydrate particulate material having a dyecovalently bonded to the surface of the alumina hydrate particle has animproved relative flex modulus as compared to the relative flex modulusof the polymer matrix without alumina hydrate particulate material. Inan embodiment, the composite has an improved relative flex modulus of atleast about 5%, such as at least 8%, at least 10%, or at least 15%,compared to the relative flex modulus of the polymer matrix withoutalumina hydrate particulate material.

In another exemplary embodiment, a composite material including apolymer matrix and an alumina hydrate particulate material having acovalently bonded dye has an improved impact strength as compared to theimpact strength of a polymer matrix having an equivalent loading ofalumina hydrate particulate material without the covalently bonded dye.As such, in certain embodiments, the composite having a polymer matrixand pigment demonstrates an improvement in impact strength of at leastabout 5%, such as at least about 8%, or at least about 10% when comparedto a composite material having an alumina hydrate particulate materialwithout a covalently bonded dye.

In a further exemplary embodiment, the relative percent crystallinity ofthe composite material is improved for composites having a particularsolids loadings content of alumina hydrate particulate material and acovalently bonded dye. According to one embodiment, a composite materialhaving a polymer matrix with a solids loading of at least 5wt % of analumina hydrate particulate material including a covalently bonded dyehas an increase in the relative percent crystallinity of at least about5% as compared to a polymer matrix without pigment. In anotherembodiment, the increase in the relative percent crystallinity is atleast about 8%, such as at least about 10%, or at least about 11% for acomposite material compared to a polymer matrix without pigment.According to a further embodiment, composite material having a greatersolids loading content, such as about 10 wt % of an alumina hydrateparticulate material, demonstrates an increase in the relative percentcrystallinity of at least about 5%, such as at least about 7% or atleast about 10% as compared to a non-composite polymer matrix.

The addition of an alumina hydrate particulate material having acovalently bonded dye to the surface of the alumina hydrate particleprovides other improved characteristics, such as higher T50. The T50 isthe temperature at which the sample has half of its original sampleweight in a thermogravimetric analysis. In an exemplary embodiment, theT50 of a composite containing a polymer matrix incorporating an aluminahydrate particulate material having a covalently bonded dye is improvedcompared to a non-composite polymer matrix. According to one embodiment,a composite containing a polymer matrix incorporating an alumina hydrateparticulate material with a covalently bonded dye has an increased T50of at least about 1%, such as at least about 3%, or at least about 10%compared to a non-composite polymer matrix.

EXAMPLES Example 1

Pigment synthesis

A boehmite particulate material, processed as described above, isprovided as the alumina hydrate particulate matter. The boehmite has aneedle-shaped morphology and is loaded into an aqueous solvent to form aboehmite sol having a solids loading of about 15wt % boehmite. The pH ofthe boehmite sol is acidic and maintained in a range of about 3.0 to4.0, while the sol is heated to a temperature of about 60° C. to 70° C.and mixed.

A dye solution is formed by combining 0.5 grams of a triazine dye havinga sulfatoethylsulfone functional group in 400 ml of deionized water. Thedye solution is heated to a temperature of about 60° C. to 70° C. andmixed.

The dye solution is added to the boehmite sol while mixing is continuedfor about 2 hours at a temperature of 60° C. to 70° C. to form a pigmentsol. After mixing, the pigment sol is cooled, excess liquid is decantedand the pigment sol is dried either by freeze drying or rotary drumdrying to form a pigment powder. The pigment powder is then milled in aball mill for about 2 hours to break up agglomerates.

Example 2

Composite

The pigment powder is compounded with a polypropylene polymer matrix.Compounding is performed in a 30 mm, 40:1 L/D, ZSK-30co-rotatingintermeshing twin extruder by Werner & Pfleidered, running at 400 rpm.Zone temperature set points incrementally increase from 388° F. at afirst zone to 450° F., with the die temperature set at 450° F.Polypropylene in powder form is mixed with red dye boehmite, which maybe formed from needle-shaped boehmite and CIBACROM HD200% in accordancewith the method of Example 1, in a plastic bag. The mixture is placed ina feed hopper of the twin extruder and the feed rate is approximately 20lb/hr.

Samples are formed through molding using a Van Dorn 120HT machine, whichis equipped with a standard 3-zone screw with a diameter of 38 mm(1.5in) and a compression ratio of 3:1. At the tip of the screw is acheck ring to reduce backflow during injection. The barrel is heatedelectrically by three heater bands and the nozzle is also heated by aheater band. The temperature profile increases from 380OF at the feedthroat to 440° F. at the nozzle.

The mold is water cooled to 80° F. A clamping force is set toapproximately 78 tons. The dosage size is 1.1 inches, which relates toan actual injection volume of approximately 1.7 cuin. After injection,the hold pressure is approximately 1000-1200 psi and the hold time isapproximately 10 seconds.

Referring to FIG. 1, the composite including polypropylene and aneedle-shaped boehmite having a covalently bonded dye, exhibits improvedrelative flex modulus compared to the relative flex modulus ofpolypropylene. As illustrated in FIG. 1, a composite having 3 wt %pigment demonstrates approximately a 15% increase and a 10 wt % pigmentillustrates an increase of the relative flex modulus of approximately21% compared to the polypropylene without pigment.

In an exemplary embodiment, the pigmented polypropylene exhibitsimproved impact strength. For example, referring to FIG. 2, the impactstrength of a composite including polypropylene and various solidsloading of boehmite having covalently bonded dye is compared to theimpact strength of a composite including polypropylene and boehmitewithout the covalently bonded dye. As illustrated in FIG. 2, each of thecomposites incorporating the dye demonstrates an improved impactstrength over samples of equivalent solids loading of boehmite withoutthe covalently bonded dye.

In a particular embodiment, composites including polypropylene andpigment exhibit increased relative percent crystallinity. Referring toFIG. 3, the relative percent crystallinity of polypropylene is comparedto the relative percent crystallinity of composites includingpolypropylene and various loading percentages of boehmite with acovalently bonded dye. As illustrated in FIG. 3, the composite materialhaving 5 wt % of boehmite and a covalently bonded dye demonstrates anincrease in relative percent crystallinity of about 11%, and thecomposite sample containing 10 wt % of boehmite having a covalentlybonded dye demonstrates an increase in the relative percentcrystallinity of about 9% when compared to the non-compositepolypropylene sample.

Referring to FIG. 4, the T50 of polypropylene is compared to the T50 ofcomposites including polypropylene and pigment. As illustrated in FIG.4, the composite material having 3.0 wt% of pigment demonstrates anincrease in T50 of 1.29% compared to the non-composite polypropylenesample. The composite sample including 5.0 wt % pigment demonstrates anincrease in T50 of 3.22% and the sample including 10.0 wt % pigmentdemonstrates an increase in the measured T50 of 10.9% when compared tothe non-composite polypropylene sample.

Aspects of the present invention enable utilization of the boehmiteparticulate material in a wide variety of applications, such as inapplications requiring higher hardness and/or involving high temperatureprocessing, such as melt processing of fluorinated polymers. Propertiesof flame retardance, UV protection, weatherability, chemical resistance,thermal conductivity, and electrical resistance make the present pigmenta significant industrial material. Other uses include implementation asan additive to paper, as an ink absorbent in inkjet printing, as afiltration media, or as an abrasive in demanding chemical mechanicalpolishing used in the electronics industry.

While the invention has been illustrated and described in the context ofspecific embodiments, it is not intended to be limited to the detailsshown, since various modifications and substitutions can be made withoutdeparting in any way from the scope of the present invention. Forexample, additional or equivalent substitutes can be provided andadditional or equivalent production steps can be employed. As such,further modifications and equivalents of the invention herein disclosedmay occur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the scope of the invention as defined by the followingclaims.

1. A pigment comprising an alumina hydrate particulate material and adye, the dye being covalently bonded to a surface of the alumina hydrateparticulate material.
 2. The pigment of claim 1, wherein the aluminahydrate particulate material has a general composition ofAl(OH)_(a)O_(b), where 0<a≦3 and b=(3−a)/2.
 3. The pigment of claim 2,wherein the alumina hydrate particulate material comprises 1% to 38%water content by weight.
 4. (canceled)
 5. (canceled)
 6. (canceled) 7.(canceled)
 8. The pigment of claim 1, wherein the alumina hydrateparticulate material has a longest dimension not greater than about 1000nm.
 9. (canceled)
 10. (canceled)
 11. The pigment of claim 1, wherein thealumina hydrate particulate material has an aspect ratio of at leastabout 2:1.
 12. (canceled)
 13. (canceled)
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 15. (canceled)16. (canceled)
 17. The pigment of claim 1, wherein the dye is selectedfrom the group consisting of anthracene dyes, azo dyes, acridine dyes,azine dyes, oxazine dyes, thiazine dyes, quinoline dyes, polymethinedyes, hydrazone dyes, triazine dyes, porphyrin dyes, porphyrazine dyes,sulfur dyes, quinacridone dyes, formazane dyes, nitro dyes, nitrosodyes, azomethine dyes, and polyol dyes.
 18. (canceled)
 19. The pigmentof claim 1, wherein the dye is covalently bonded in place of a hydrogenof a hydroxyl group on the surface of the alumina hydrate particulatematerial.
 20. A composite material comprising: a polymer matrix; and apigment dispersed in the polymer matrix, the pigment comprising analumina hydrate particulate material and a dye, the dye being covalentlybonded to a surface of the alumina hydrate particulate material.
 21. Thecomposite material of claim 20, wherein the alumina hydrate particulatematerial has a general composition of Al(OH)_(a)O_(b), where 0<a≦3 andb=(3−a)/2.
 22. (canceled)
 23. (canceled)
 24. The composite material ofclaim 20, wherein the alumina hydrate particulate material has a longestdimension not greater than about 1000 nm.
 25. (canceled)
 26. Thecomposite material of claim 20, wherein the alumina hydrate particulatematerial has an aspect ratio of at least about 2:1.
 27. (canceled) 28.The composite material of claim 20, wherein the alumina hydrateparticulate material comprises primarily one of platelet-shapedparticles, needle-shaped particles, and an ellipsoidal-shaped particles.29. The composite material of claim 20, wherein the dye is selected fromthe group consisting of anthracene dyes, azo dyes, acridine dyes, azinedyes, oxazine dyes, thiazine dyes, quinoline dyes, polymethine dyes,hydrazone dyes, triazine dyes, porphyrin dyes, porphyrazine dyes, sulfurdyes, quinacridone dyes, formazane dyes, nitro dyes, nitroso dyes,azomethine dyes, and polyol dye.
 30. (canceled)
 31. (canceled)
 32. Thecomposite material of claim 20, wherein the composite materialscomprises about 2 wt % to about 25 wt % of the pigment based on thetotal weigh of the composite material.
 33. (canceled)
 34. (canceled) 35.The composite material of claim 20, wherein the polymer matrix isselected from the group consisting of polyolefins and halogenatedpolyolefins.
 36. (canceled)
 37. (canceled)
 38. The composite material ofclaim 20, wherein the composite material has a relative flex modulusincrease of at least about 5% compared to a relative flex modulus of thepolymer matrix without alumina hydrate particulate material. 39.(canceled)
 40. The composite material of claim 20, wherein the compositematerial has an impact strength at least about 5% higher than thecomposite material having an equivalent loading of alumina hydrateparticulate material without covalently bonded dye.
 41. (canceled) 42.(canceled)
 43. (canceled)
 44. (canceled)
 45. (canceled)
 46. (canceled)47. (canceled)
 48. (canceled)
 49. (canceled)
 50. (canceled) 51.(canceled)
 52. (canceled)
 53. A method of forming a pigment, the methodcomprising: providing a slurry comprising an alumina hydrate particulatematerial; and adding a dye and the slurry to form a pigment slurry, thedye including a functional group configured to facilitate covalentbonding with a surface group of the alumina hydrate particulatematerial.
 54. The method of claim 53, wherein providing the slurrycomprises providing not greater than about 30 wt % of the aluminahydrate particulate material in an aqueous solution.
 55. (canceled) 56.(canceled)
 57. (canceled)
 58. (canceled)
 59. (canceled)
 60. (canceled)61. (canceled)
 62. (canceled)
 63. The method of claim 53, whereinproviding a slurry comprises providing a slurry having a pH not greaterthan about 7.0.
 64. (canceled)
 65. (canceled)
 66. (canceled)
 67. Themethod of claim 53, further comprising forming a dye solution of notgreater than about 10 wt % of a dye in an aqueous solution; and whereinadding the dye comprises adding the dye solution.
 68. (canceled) 69.(canceled)
 70. (canceled)
 71. (canceled)
 72. (canceled)
 73. (canceled)74. The method of claim 53, wherein facilitating covalent bondingincludes facilitating nucleophilic substitution.
 75. (canceled) 76.(canceled)
 77. (canceled)
 78. (canceled)
 79. (canceled)
 80. (canceled)81. (canceled)
 82. (canceled)
 83. (canceled)